diff --git a/packages/core/src/core/client.telemetrySwap.test.ts b/packages/core/src/core/client.telemetrySwap.test.ts
index 4712bd468c4..2a19bc70754 100644
--- a/packages/core/src/core/client.telemetrySwap.test.ts
+++ b/packages/core/src/core/client.telemetrySwap.test.ts
@@ -93,6 +93,11 @@ function makeEnv() {
       sessionId = id;
       resumedData = data;
     },
+    // `initialize()` calls restoreLoadedSkillsFromHistory, which resolves the
+    // SKILL tool through the registry; this mock only exercises the telemetry
+    // swap, so return an empty registry (no SKILL tool → the restore is a
+    // no-op) rather than let the call throw `getToolRegistry is not a function`.
+    getToolRegistry: () => ({ getTool: () => undefined }),
   };
   const client = new GeminiClient(config as Config);
   const fakeChat = {